Recyclable polymer and process for production thereof

ABSTRACT

A novel resin is provided which is renewable with less energy. A process for renewing the resin is also provided. The present invention includes a polymer having the repeating unit represented by Structural Formula (1) below, and a process for producing the polymer: [—P 1 —R—] n  (1). In the formula, P 1  indicates an addition polymer moiety having a continuous hydrocarbon chain as the skeleton containing no condensation system, and is a polymer or oligomer prepared by addition polymerization of one or more monomers having a double bond; R indicates a linking group constituted of a condensation system for linking the polymer moieties P; and n is a number of repeating units and is an integer of 2 or more.

This application is a division of application Ser. No. 10/443,089, filedMay 22, 2003, which is a continuation of International Application No.PCT/JP02/13381, filed Dec. 20, 2002, which claims the benefit ofJapanese Patent Application Nos. 389887/2001, filed Dec. 21, 2001,389895/2001, filed Dec. 21, 2001, and 368037/2002 filed Dec. 19, 2002.All prior applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Filed of the Invention

The present invention relates to a novel polymeric material, which canbe reused by decomposition and re-synthesis. Also, the present inventionrelates to a novel process for decomposition-repolymerization of apolymeric material, and to a novel system of material circulation.

2. Related Background Art

Through the years, various novel materials, which are useful in everydaylife and industry, have been developed successively by coal chemicaltechniques and by petrochemical techniques. Typical examples includeplastic materials such as polyethylene, polypropylene, polystyrene andpolyvinyl chloride; and rubbers such as polyisoprene and polybutadiene.Recently, resin materials having unique properties have been developedsuch as polyimide resins having excellent heat resistance and highimpact strength, and entirely-aromatic liquid crystalline polymers.

However, such polymers are reused seldom. The polymers after disposal aswaste materials will remain in the environment to impose heavy burden tothe global environment. Waste materials from activities of industriesand living are becoming serious as the social problems because ofshortage of dumping sites, undesirable generation of dioxins onincineration, increase in carbon dioxide concentration in the air, andso forth. At the moment, development of materials and products inconsideration of the global environment is being expected in connectionwith the carbon dioxide gas emission quotas, and waste materials. It isconsidered to be necessary to develop a technique which minimizes theconsumption of the global resources to maintain the global environment.

In recent years, to meet the above problems, techniques have beendeveloped for reuse of polymeric materials: for example, reuse techniquesuch as reuse of used plastic parts after simple washing, and reworkingof used resins for other uses of different added value; a materialrecycling technique such as molding of a used resin and a virgin resinin a sandwich state as described Japanese Patent Publication No.6-24739; chemical recycling techniques such as decomposition of a usedresin into a monomer after cutting into pieces; and thermal recyclingtechnique such as use of waste resin as a fuel.

However, of such material recycling techniques, the reuse technique islimited to the use as the same parts. The material recycling techniquehas problems as to the stability of the properties owing todeterioration of the material, guarantee of the products, deteriorationof appearance, and so forth. The use thereof is limited to lower gradearticles practically. The chemical recycling technique is limited in thekinds of applicable materials, involving the problems of the monomeryield and a large amount of energy required for decomposition into themonomer. The thermal recycling technique has problems of the combustionheat inherent to the material, and reduction of carbon dioxidegeneration. Thus no recycling technique meets the requirement of themarket. To meet these requirements, technical development of a novelresin which can be regenerated with a low energy, and a novel techniquefor regenerating the resin is wanted.

The resins are classified roughly into a condensation polymerizationtype polymers and an addition polymerization type polymers. Thecondensation polymerization type polymers typified by polyamides arereadily depolymerized at the condensation sites by an acid or base,whereas the addition polymerization type polymers such as polystyrenerequires a large amount of energy for depolymeization in an inert gasatmosphere under a high temperature.

Moreover, the decomposition products contain a mixture of dimer, trimer,tetramer, and so forth besides the monomer as described by T. Sawaguchiet al., Polym. Int. 49, 921 (2000). From the mixture, only the monomerwhich is polymerizable should be isolated, and a large amount of energyis necessary for the isolation. The yield of the recovered monomer isalso important. Some of the addition polymerization polymers such aspolypropylene cannot readily be depolymerized by the above-mentionedmethod.

Besides, decomposition of plastics using water or carbon dioxide in asupercritical state of a high temperature and a high pressure isinvestigated as described in Japanese Patent Laid-Open No. 8-72058. Sucha method is not regarded to be the best method from the standpoint ofthe large-scale treatment and the large amount of energy to be inputted.Therefore, universally applicable techniques are demanded.

At the moment, the materials and products are demanded which meet theglobal environmental problem, such as carbon dioxide gas emission quotasand waste problems. On the other hand, minimization of consumption isrequired to maintain the natural resources.

The conventional addition type polymers which are synthesized by amonomer addition reaction can be regenerated for the materialcirculation only by chemical decomposition into the monomer.

Otherwise, a polymer can be formed from lower polymer molecules shorterin length than the practical polymer molecules as a kind of chemicalparts (hereinafter the lower polymer being referred to as a “polymer”occasionally) by introducing a functional group into the parts forlinkage-and-decomposition, and synthesizing the polymer from this parts.The polymer after use as an article like a molded product can bereturned to the original chemical parts by breaking the linkage betweenthe parts. The recovered parts can be formed again into a polymer bylinking the parts together.

Specifically, a polymer (polymer) which has two condensable functionalgroups, and a molecule which has two functional groups capable oflinking with the above condensable functional groups to serve as acoupler for the polymer are employed.

An example is explained below by taking a styrene polymer. A styrenepolymer having a carboxyl group on each end of the molecule is employedas the two-functional polymer, and butanediol is employed as thecoupling molecule having two functional groups linkable with the abovefunctional groups of the polymer. These compounds are linked together bydehydration condensation in the presence of an acid catalyst to form ahigh polymer having a structure of successive linkage of the styrenepolymer and the butanediol. Each of the styrene polymer moieties andbutandiol moieties are linked by ester linkage.

The ester linkage can be broken by hydrolysis reaction into the originalstyrene polymer having a carboxyl group at the respective ends andbutanediol. Thus the reaction is reversible. The compounds thus obtainedcan be converted into a high molecular styrene polymer by the samepolycondensation reaction as above repeatedly without limitation of therepetition time basically.

SUMMARY OF THE INVENTION

Therefore,

[1] The present invention relates to Polymer (A) represented byStructural Formula (1) below:[—P₁—R—]_(n)  (1)(in the formula, P₁ indicates an addition polymer moiety having acontinuous hydrocarbon skeleton containing no condensation system andformed by addition polymerization of one or more monomers having adouble bond; R indicates a linking moiety comprised of a condensationsystem; and n is a number of repeating units and is an integer of 2 ormore).

[2] The present invention relates also to the polymer stated in Item[1], wherein the linking moiety R is selected from the group consistingof —CO—O—, —CONH—, —NH—CO—O—, and —NH—CO—NH—.

[3] The present invention relates also to the polymer stated in Item[1], wherein the linkage sites of R represented by the bond between P₁and R in the repeating unit of Structural Formula (1) are the samethroughout the repeating units.

[4] The present invention relates also to the polymer stated in Item[1], wherein the linkage sites of R represented by the bond between P₁and R in the repeating unit of Structural Formula (1) are differentbetween the adjacent repeating units.

[5] The present invention relates also to the polymer stated in Item[1], wherein the linkage sites of R represented by the bond between P₁and R in the repeating unit of Structural Formula (1) are selected atrandom from the linkage sites of R.

[6] The present invention relates also to the polymer stated in any ofItems [1], [3], [4] and [5], wherein the linking moiety R is representedby Structural Formula (2) below:X1-A-X2  (2)(in the formula, X1 and X2 are respectively an atomic group linked to P₁in Structural Formula (1), and A is an atomic group capable of linkingwith X1 and X2).

[7] The present invention relates also to the polymer stated in Item[6], wherein X1 and X2 are selected respectively from the groupconsisting of —CO—O—, —CON H—, —NH—CO—O—, and —NH—CO—NH—.

[8] The present invention relates also to the polymer stated in Item[6], wherein X1 and X2 are the same atomic group.

[9] The present invention relates also to the polymer stated in Item[7], wherein the same atomic groups X1 and X2 are respectively —CONH—.

[10] The present invention relates also to the polymer stated in Item[6], wherein the atomic groups X1 and X2 are different from each other.

[11] The present invention relates also to the polymer stated in Item[10], wherein the linkage site of X1 and/or X2 to A is selected atrandom from plural linkage sites of X1 and X2, respectively.

[11′] The present invention relates also to the polymer stated in Item[10], wherein the linkage sites of X1 and/or X2 to A are the samethroughout the repeating units.

[11″] The present invention relates also to the polymer stated in Item[10], wherein the linkage sites of X1 and/or X2 to A are different fromeach other in the adjacent repeating units.

[12] The present invention relates also to the polymer stated in Item[1], wherein the addition polymer moiety P₁ is at least one moietyselected from the group consisting of polystyrene, polybutadiene,polyacrylonitrile, polyethylene and polypropylene.

[13] The present invention relates also to the polymer stated in Item[6], wherein the group A is an alkylene group.

[14] The present invention relates also to the polymer stated in Item[13], wherein the alkylene group has a phenyl group on a side chain.

[15] The present invention relates also to the polymer stated in Item[13], wherein the alkylene group has a phenylene group in the mainchain.

[16] The present invention relates also to the polymer stated in Item[5], wherein the group A is a phenylene group.

In the above description, the process of depolymerization for cuttingselectively the linkage in the linking moiety R, and a process formolding the polymer is assumed to be conducted under relatively mildconditions.

Under severer conditions, the polymer molecules can be cut by variousstresses exerted to the polymer molecules in some cases. Such cutting ofthe molecules does not give the original two-functional polymer afterthe hydrolysis, but can give a molecule having a reactive functionalgroup on the one end only of the molecule. Such a molecule serves as areaction-terminating agent to retard the growth of the molecule, whichcan prevent formation of a sufficiently high-molecular polymer.

In such a case, a compound (B) is added which has a condensablefunctional group and a spin-trapping group. With this compound, when thepolymer (A) is cut inside the addition polymer moiety P₁, the compound(B) reacts with the polymer (A) to introduce the condensable functionalgroup to the end of the molecule of the polymer (A). (Incidentally, theterm “polymer” in the present invention is used occasionally forindicating a composition of the polymer represented by StructuralFormula (1) containing another substance.)

Therefore,

[17] The present invention relates to a composition containing mixedly apolymer stated in Item [1], and a compound having a condensablefunctional group and a spin-trapping group.

[18] The present invention relates also to the composition stated inItem [17], wherein the polymer is a condensate of P₁ and R.

[19] The present invention relates also to the composition stated inItem [17], wherein the compound having a condensable functional groupand a spin-trapping group is represented by Structural Formula (3):X₃-M₁-X₄  (3)(in the formula, X₃ is a condensable functional group; X₄ is aspin-trapping group; M₁ is selected from the group consisting of—(CH₂)_(n2)—, —C₆H₄— and —(CH₂)_(m1)—C₆H₄—(CH₂)_(m2)—(n2, m1 and m2 arerespectively an integer from 1 to 8, and —C₆H₄— represents a phenylenegroup).

[20] The present invention relates also to the composition stated inItem [19], wherein the compound having a condensable functional groupand a spin-trapping group is a nitroso compound.

[21] The present invention relates to a molded article formed by moldingthe polymer stated in Item [1].

[22] A process for producing the polymer represented by StructuralFormula (1), comprising condensation-polymerizing an addition-polymerhaving a functional group at each end thereof solely or in a manner ofmaking a two-functional compound intervening therebetween:[—P₁—R—]_(n)  (1)(in the formula, P₁ indicates an addition polymer moiety havingcontinuous hydrocarbon skeleton containing no condensation system andformed by addition polymerization of one or more monomers having adouble bond; R indicates a linking moiety comprised of a condensationsystem for linking plural P₁ moieties; and n is a number of repeatingunits and is an integer of 2 or more).

[23] The present invention relates also to the process for producing thepolymer stated in Item [22], wherein the process further comprisesadding a compound having a condensable functional group and aspin-trapping group to the polymer represented by the above StructuralFormula (1).

[24] The present invention relates also to the process for producing thepolymer stated in Item [23], wherein the polymer represented by theabove Structural Formula (1) is one stated in any of Items [2] to [16],[35], and [36].

[25] The present invention relates also to the process for producing thepolymer stated in Item [23], wherein the compound having the condensablefunctional group and the spin-trapping group is represented byStructural Formula (3):X₃-M₁-X₄  (3)(in the formula, X₃ is a condensable functional group; X₄ is aspin-trapping group; and M₁ is selected from the group consisting of—(CH₂)_(n2)—, —C₆H₄— and —(CH₂)_(m1)—C₆H₄—(CH₂)_(m2)— (n2, m1, and m2are respectively an integer from 1 to 8).

[26] The present invention relates also to the process for producing thepolymer stated in Item [22], wherein the process further comprises astep of molding the polymer represented by the above Structural Formula(1).

[27] The present invention relates to a method for treating the polymercomprising a step of providing the polymer represented by StructuralFormula (1) below, and a step of depolymerizing the polymer by cuttingselectively a linkage in the linking moiety R:[—P₁—R—]_(n)  (1)(in the formula, P₁ indicates an addition polymer moiety having acontinuous hydrocarbon skeleton containing no condensation system andformed by addition polymerization of one or more monomers having adouble bonds; R indicates a linking moiety comprised of a condensationsystem for linking the plural P₁ moieties; and n is a number ofrepeating units, and is an integer of 2 or more).

[28] The present invention relates also to the method for treating thepolymer stated in Item [27], wherein the method comprises further a stepof condensing the substance obtained by the depolymerization into apolymer.

[29] The present invention relates also to the method for treating thepolymer stated in Item [27], wherein the method further comprises a stepof molding the polymer obtained.

[30] The present invention relates also to the method for treating thepolymer stated in Item [27], wherein the method comprises further a stepof dissolving the polymer in a solvent before the depolymeization step.

[31] The present invention relates also to the method for treating thepolymer stated in Item [27], wherein the linking moiety R is representedby Structural Formula (2) below, and at least one of the bonds of X1 andX2 is cut:X1-A-X2  (2)(in the formula, X1 and X2 are respectively an atomic group linkable tothe end of P₁ in Structural Formula (1), and A is an atomic grouplinkable to X1 and X2).

[32] The present invention relates also to the method for treating thepolymer stated in Item [27], wherein the method further comprises a stepof depolymerizing the polymer represented by the above StructuralFormula (1) by addition of a compound having a condensable functionalgroup and a spin-trapping group, and a step of condensing the substanceobtained by the above depolymerization step to obtain a polymer again.

[33] The present invention relates also to the method for treating thepolymer stated in Item [32], wherein the polymer represented by theabove Structural Formula (1) is any of the polymers stated in Items [2]to [16], [11′ ], and [11″].

[34] The present invention relates also to the method for treating thepolymer stated in Item [32], wherein the compound having a condensablefunctional group and a spin-trapping group is represented by StructuralFormula (3) below:X₃-M₁-X₄  (3)(in the formula, X₃ is a condensable functional group; X₄ is aspin-trapping group; and M₁ is selected from the group consisting of—(CH₂)_(n2)—, —C₆H₄— and —(CH₂)_(m1)—C₆H₄—(CH₂)_(m2)— (n2, m1, and m2are respectively an integer from 1 to 8).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows molecular weight distribution (differential curve) by GPCof the polymer obtained in Example 10.

FIG. 2 shows the results of FT-IR measurement of the polymer obtained inExample 10.

FIG. 3 shows the results of measurement of thermal decompositioncharacteristics of the polymer obtained in Example 10.

FIG. 4 shows molecular weight distribution (differential curve) by GPCof the polystyrene polymer decomposed and recovered in Example 35.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is described below in detail.

(Polymer)

The essential compound in the present invention is the polymerrepresented by Structural Formula (1):[—P₁—R—]_(n)  (1)In the formula, P₁ indicates an addition polymer moiety having acontinuous hydrocarbon skeleton, namely a moiety of a polymer oroligomer formed by addition polymerization of one or more kinds ofdouble bond-containing monomers; R indicates a linking moietyconstituted of a condensation system for linking plural P₁ moieties; andn is a number of the repeating units and an integer of 2 or more. Forselective depolymerization at the portion R, the P₁ moiety should notcontain a condensation system such as ester linkage (mentioned later).The linking moieties R are classified roughly into two types. The typesof the polymer depending on the linking moiety are explained accordingto the linking mode.(Linking Mode 1)

In a first preferred mode, the addition polymer moieties P₁ are linkeddirectly by a dissociable linkage without a spacer, the exampleincluding linkage of the polymer moieties P₁ by ester linkage (—COO—),amide linkage (—CONH—), urethane linkage (—NH—COO—), urea linkage(—NH—CO—NH—), and the like. In such a mode of linkage, the orientationdirection of the linkage in the main chain may be the same along themain chain throughout the repeating units, or may be reversedalternately between the adjacent repeating units. For example, [1] in afirst case, the polymer P₁ has a carboxyl group introduced to one endand an amino group introduced to the other end (the linkage direction inthe main chain is the same throughout the repeating units), and [2] in asecond case, a kind of polymer P₁ having a carboxyl group at therespective ends and another kind of the polymer having an amino group atthe respective ends are linked together (the direction of the linkage isreversed alternately between the adjacent repeating units).

(Linking Mode 2)

In a second preferred mode, the linking moiety R is derived from a lowermolecular compound represented by Structural Formula (2):X1-A-X2  (2)In the formula, X1 and X2 are respectively an atomic group capable oflinking to the end of the addition polymer P₁, and A is a spacermentioned later.

The groups X1 and X2 are dissociable, and preferably are any oneselected respectively from ester linkage (—COO—), amide linkage(—CONH—), urethane linkage (—NH—COO—), urea linkage (—NH—CO—NH—). Ofthese the amide linkage is particularly preferable. In this linkingmode, X1 and X2 may be identical, or X1 and X2 are different from eachother. The combination of X1 and X2 is selected depending on ease of theavailability and convenience in the depolymerization mentioned later.

In the case where X1 and X2 are different from each other, thearrangement of X1 and X2 may be the same throughout the repeating units,or may be reversed alternately between the adjacent repeating units. Forexample, condensation of the polymer P₁ having a carboxyl group onrespective ends with ethanolamine, two types of linkage are possible:[1] one end of P₁ is amide, and the other end thereof is ester, and [2]the both end of P₁ is amide or ester. The type of the linkage isselected in consideration of reaction efficiency in the synthesis andthe convenience in depolymerization mentioned later.

In the case where X1 and X2 are identical, X1 and X2 are dissociable(reversibly reactive). In this case, the orientation direction of thelinkage may be the same throughout the repeating units, or reversedalternately between the adjacent repeating units. The type of thelinkage is selected in consideration of the availability of the sourcematerials and the convenience in the depolymeization mentioned later.For example, in the case where a polymer P₁ having a carboxyl grouprespectively at the both ends is condensed with ethanol amine, [1] P₁may have an amide linkage on one end and an ester linkage at the otherend, or [2] P₁ may have an amide linkage at the respective ends or anester linkage at the respective ends of P. The types of the linkage isselected in consideration of reaction efficiency in the synthesis andthe convenience in depolymerization mentioned later.

(Composition of Respective Constituting Components)

The addition polymer moiety P₁ includes specifically polymer moietiesconstituted of polystyrene, polybutadiene, polyacrylonitrile,polyethylene and polypropylene, and copolymers thereof. The additionpolymer moiety P₁ should not contain condensation system like esters andamides. The polymerization degree of the polymer moiety is selected inview of the molecular weight of the entire polymer and the content ofthe dissociable linkage, the mechanical strength and other properties,and the ease of depolymerization. Accordingly, the range thereof cannotbe decided definitely, but is preferably 2, or more, more preferably inthe range from 2 to 2000 practically in view of the synthesis process.

The spacer A in the above Linking Mode 2 includes preferably those whichdo not impair the properties of the polymer P₁. The spacer A may be analiphatic group such as an alkylene of 1-14 carbons, or an aromaticgroup, but is preferably a group containing at least an aromatic moietyin view of the water-resistance and the polymerization reactivity. Inparticular, for the block having an aromatic ring like polystyrene,preferred are an alkylene having a phenyl in the side chain (e.g.,—CHPh-CH₂—), an alkyene having a phenylene in the main chain (e.g.,—CH₂-Ph-CH₂—), and a phenylene (-Ph-).

On the other hand, the linkage moiety having the spacer A includescompounds having at least one aromatic moiety such asp-phenylenediamine, m-phenylenediamine, p-xylenediamine,m-xylenediamine, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether,4,4′-diaminodiphenylmethane, 3,4′-diaminodiphenylmethane,4,4,-diaminodiphenylsulfone, 2-(4-aminophenyl)ethylamine, and2,2′-dithiodianiline.

The spacer A includes also moieties of aliphatic compounds such as3,3′-diaminopropylamine, and 2,2′-diaminodiethyl ether.

(Production Process)

The polymer of the present invention is synthesized by condensing acompound having a functional group on the respective both ends singly orwith a bifunctional compound. Specifically, in Linking Mode 1, anaddition polymer P having a functional group, such as an amino group anda carboxyl group, at the respective both ends, and the functionalizedpolymer is condensed in a molten state or in a solution, and ifnecessary, by using a catalyst or an active intermediate. In LinkingMode 2, similarly, the compound P₁ functionalized at the both ends and abifunctional compound (a source material giving the moiety representedby Structural Formula (2)) are condensed. The molecular weight of thefinal polymer is preferably in the range of 10⁴ to 10⁶.

(Molded Article)

The polymer of the present invention can be molded into molded resinarticles similar to the high polymer of the constituting additionpolymer component. That is, the resin produced from the thermoplasticpolymer P₁ component can be molded by a conventional molding processsuch as compression molding, extrusion molding, and injection molding,whereby a novel recyclable molded resin article can be provided asdescribed below. The molded article may contain a plasticizer, acolorant, a filler, a stabilizer, and a flame retardant, provided thatthe recycling is not prevented.

(Depolymerization and Recycling)

The polymer of the present invention can be depolymerized by cuttingselectively the dissociable linkage in the coupling moiety to obtain are-condensable parts. The depolymerization can be conducted with arelatively small energy input, since the depolymerization is conductedby cutting the disociable linkage. The reaction utilized for thedepolymerization is not specially limited. Readily practicable ishydrolysis reaction. For example, a molded article itself after use, ora flaked article thereof is subjected to hydrolysis with an acid oralkali catalyst under mild conditions for depolymerization of thelinkage. The depolymerization facilitates removal of deterioratedportions and removal of an additive, enabling recovery of the recyclingsource material in a more refined state.

In Linking Mode 2, two cutting methods are applicable: in one method,both X1 and X2 in the coupling moiety R are cut; and in the othermethod, only one of the two is cut. In the latter method, the linkinggroups X1 and X2 are preferably different from each other. The selectivecutting of one of the linking groups is advantageous in the case wherethe orientation of X1 and X2 is the same throughout the repeating units,since the depolymerization gives the repeating units as a simpleproduct, thereby facilitating treatment for the purification andrecondensation.

The depolymerization product is regenerated by recondensation withoutpreliminary treatment or modified for reactivity, if necessary, into theoriginal polymer (1). The polymer can be formed into molded articles. Tomeet the necessity, the condensation degree (n in Structural Formula(1)) may be changed, or the linking mode may be changed to control thephysical properties.

(Addition of Spin-Trapping Compound)

To attain the object of the present under severe conditions such thatthe cutting occurs within the addition polymer moiety P₁, Compound (B)is preferably added which has a spin-trapping function. By reaction ofPolymer (A) and Compound (B), a condensing functional group isintroduced to the molecular end of the Polymer (A).

The addition of Compound (B) having a spin-trapping function is known.For example, Japanese Patent Application Laid-Open No. 9-176372discloses addition of an isoxazolidinone compound for the purpose ofstabilization of melt flow and prevention of discoloration; and JapanesePatent Application Laid-Open No. 7-324028 discloses addition of aspin-trapping compound to a cosmetic or dermatologic composition for thepurpose of light protection, aging prevention, and/or acne treatment.These intend to prevent oxidation deterioration of matrix materials bytrapping of peroxide radicals formed by action of oxygen or oxidation byuse of the spin-trapping compound. These disclosures intends to preventdeterioration of a material, and not to restoration of a polymermolecules, and is not effective for such purposes.

On the other hand, the mechanism in the present invention is asdescribed below. On cutting of a polymer by external stress, freeradicals are formed at the cut site. A compound (B) having a condensablefunctional group and a spin-trapping group, if coexists, traps freeradical, and consequently the condensable functional group of Compound(B) is introduced to the end of the cut end of the polymer.

The compound (B) having a condensable functional group and aspin-trapping group is represented by Structural Formula (3):X₃-M₁-X₄  (3)Where X₃ is a condensable functional group, X₄ is a spin-trapping group,and M₁ is the groups represented by Structural Formula (4):

where n2, m1 and m2 are respectively an integer of 1 to 8, and thelinking site on the aromatic ring may be an ortho position or a metaposition differently from the para position shown in the formulas.

The condensable functional group X₃ is a usual condensable functionalgroups such as carboxyl, hydroxyl, and amino. The spin-trapping group X₄is preferably a nitroso-containing group. The nitroso group-containingcompound is exemplified by the compound represented by StructuralFormula (5).

Otherwise, paranitrosodurene derivatives are useful also.

The restoration of a molecule by the above reaction is useful, forexample, in the process below. Firstly, in a system in which theaddition polymer having a condensable functional group at the respectiveends of the molecule is used for repeatedpolymerization-depolymerization, especially, in the depolymerizationstep, the molecule can be cut by agitation or a like operation. In thisstep, the compound having a condensable functional group and aspin-traping group, if present, will trap the radical formed by thecutting by the spin-trapping group. In this process, if the oxygenpresent in the polymer solution when the molecule is cut, the reactiveoxygen reacts selectively with the radical formed by cutting to formunwanted peroxide radical. Therefore, the oxygen should be removedcompletely from the solution by bubbling an inert gas like nitrogen intothe solution, and the reaction itself should be conducted in an inertgas atmosphere.

Next, in a process in which the high polymer obtained by thepolymerization is molded, a compound having a condensable functionalgroup and a spin-trapping group is preferably mixed into the polymerpreliminarily. In the molding machine, heat and a shearing stressapplied to the resin cause scission of the molecular chain, but theradical formed by molecular scission is trapped even in the solid phaseby the spin-trapping group.

The concentration of the compound having the condensable functionalgroup and the spin-trapping group to be mixed ranges, in the former caseof the solution reaction, preferably from 0.01% to 5%, more preferablyfrom 0.1% to 3% based on the source resin, and in the latter case of thesolid operation, ranges preferably from 0.1% to 5% since the movement ofthe molecule is restricted in the solid phase in comparison with thereaction in the solution.

As described above, in the technique of polymerization-depolymerizationusing a polymer having two functional groups and a coupling compoundcapable of linking to the two functional group, the addition of acompound having a condensable functional group and a spin-trapping groupcan improve the reproducibility of the repetition, and reliability ofthe reaction such as the yield, purity, and properties of the resin.With this technique, the regeneration cycles can be increasedsignificantly. That is, the resin used as molded articles or packagingmaterials can be recovered and depolymerized for reuse as the sourcematerial of the resin. Thus the regenerated resin produced by therepolymerization is useful without lowering the level of the usage. Suchtechnique will change greatly the recycle techniques which are limitedin application.

Moreover, the technique of the present invention can be combined withvarious conventional techniques such as reuse techniques for moldedarticles, material recycling techniques for sandwich molding, chemicalrecycling techniques of decomposition of a resin to the source monomer,and thermal recycling technique of utilizing heat of combustion, and soforth, without limiting the material recycling model.

EXAMPLES

The present invention is described below specifically without limitingthe present invention.

Example 1 Synthesis of Ester-Linked Polymer Having Spacer, 1

In a flask, were placed 2 g of 1,4-butanediol, and 5 g of a polystyrenehaving a carboxylic acid group at the respective ends (Mw: 25,000,produced by Scientific Polymer Product Co,; Mw indicates aweight-average molecular weight). The mixture was heated to 180° C. in anitrogen atomosphere. Thereto was added 35 mg of tetraisopropylorthotitanate diluted with 100 μL of toluene, and the mixture wasstirred. Then the mixture was kept at a temperature of 180-200° C. toremove the water formed and the diol by distillation. The reaction wascontinued under a reduced pressure to the final pressure of 6.67 kPa.The reaction product was taken out in a hot state from the flask toobtain a polymer in a white wax state (Compound No. A-1).

The molecular weight was measure by gel permeation chromatography(herein after referred to as “GPC”) under the measurement conditionsshown below.

-   -   Measurement apparatus: HLC 8120 GPC (Tosoh Corp.)    -   Columns: TSKgel SuperHZM-M+HZM-N    -   Elution Liquid: THF, 40° C.    -   Standard: Polystyrene (Polymer Laboratories Co.)

The weight-average molecular weight of the resulting polymer was400,000, and therefore the number (n) of the repeating units isestimated to be about 16.

Examples 2 to 5 Syntheses of Ester-Linked Polymer Having Spacer, 2 to 5

The synthesis was conducted under the same conditions as in Example 1except that the polymer moiety (P) of the polystyrene (PS) having acarboxyl group at the respective ends was replaced by a moiety ofpolystyrene of a different molecular weight, polypropylene, orpolyethylene (PE); and 1,4-butanediol was replaced by another diol.

Table 1 below shows Examples 1 to 5 specifically.

For simplicity of representation, Synthesis Example 1 is summarized asA-1 in the table, in which the ester-linked polymer of the number ofrepeating units (n) of 16 was prepared from 1,4-butanediol and thepolystyrene having a carboxylic acid group at the both ends (Mw: 25,000,Mw representing weight-average molecular weight). Examples 2 to 5 aresummarized in the same style. TABLE 1 Example Compd R No. No. P (Mw) X1A X2 n 1 A-1 PS COO 1,4-C₄H₈ OCO 16 (25,000) 2 A-2 PS (15,000) COO

OCO 4 3 A-3 PP COO 1,8-C₈H₁₆ OCO 70 (5,000) 4 A-4 PE COO 2,5-C₆H₁₂ OCO 9(50,000) 5 A-5 PS (100,000) COO

OCO 3

Example 6 Synthesis of Amide-Linked Polymer Having Spacer, 1

A 5-gram portion of polystyrene dicarboxylic acid having a carboxylgroup at the respective ends (Mw: 15,000) was suspended in 100 mL ofethanol. To this suspension, was added a solution of 0.2 g ofhexane-1,6-diamine in 10 mL ethanol. The mixture was stirred at roomtemperature. Thereby white percipitate was formed with heat generation.After completion of the reaction, the crystalline matter was collectedby filtration, and washed with ethanol twice to obtain a nylon salt. A3-gram portion of this nylon salt was placed in a flask, and afterpurging with nitrogen, the salt was heated with gradual evacuation tomelt the salt. The content in the flask became viscous gradually to forma pale yellow opaque polymer (Compound No. B-1).

The resulting polymer had a weight-average molecular weight of 465,000according to GPC measurement, and the number of the repeating units (n)was estimated to be about 31.

Examples 7 to 9 Synthesis of Amide-Linked Polymer Having Spacer, 2 to 4

Polymers were prepared under the same conditions and in the same manneras in Example 6 except that the polymer moiety (P) of the polystyrene(PS) having the carboxyl groups at the respective ends was changed topolystyrene of different molecular weight or polypropylene (PP), and thehexane-1,6-diamine was changed to another diol compound.

Table 2 below shows Examples 6 to 9 specifically.

For simplicity of representation, Synthesis Example 6 in which theamide-linked polymer of the number of repeating units (n) of 31 wasprepared from hexane-1,6-diamine and the polystyrene having a carboxylgroup at the respective ends (Mw: 15,000, Mw representing weight-averagemolecular weight) is summarized as B-1 in the table. Examples 7 to 9 aresummarized in the same style. TABLE 2 Example Compd R No. No. P (Mw) X1A X2 n 6 B-1 PS CONH 1,6-C₆H₁₂ NHCO 31 (15,000) 7 B-2 PS CONH 1,3-C₆H₆NHCO 7 (100,000) 8 B-3 PP CONH 2,5-C₅H₁₀ NHCO 24 (50,000) 9 B-4 PE(2,000) CONH

NHCO 10

Example 10 Synthesis of Amide-Linked Polymer Having Spacer, 5

In a flask equipped with a nitrogen-introducing tube and a stirrer, wereplaced 5.0 g (0.2 mmol) of PS dicarboxylic acid having Mw of 25,000;40.05 mg (0.2 mmol) of 4,4′-diaminophenyl ether; 248 mg (0.8 mmol) oftriphenyl phosphite; and 30 mg of lithium chloride. The mixture in theflask was dissolved in 2 mL of N-methylpyrrolidone (NMP) and 0.2 mL ofpyridine. The solution was stirred at 100° C. for one hour in a nitrogenatmosphere. The resulting polymer solution was poured into 200 mL ofmethanol, and the deposited polymer was collected by filtration. Thecollected polymer was refluxed in 100 mL of methanol for one hour toremove the remaining solvent and condensing agent. Then the polymer wascollected by filtration and was dried in vacuo to obtain a white fibrouspolymer (Compound No. B-5).

The molecular weight was measure by GPC under the measurement conditionsshown below.

-   -   Measurement apparatus: HLC 8120 GPC (Tosoh Corp.)    -   Columns: TSKgel SuperHZM-M+HZM-N    -   Elution Liquid: THF, 40° C.    -   Standard: Polystyrene (Polymer Laboratories Co.)

The weight-average molecular weight of the resulting polymer was370,000, and the number (n) of the repeating units is estimated to beabout 11. FIG. 1 shows the molecular weight distribution (differentialcurve) as measured by GPC. In FIG. 1, curve 1 corresponds to the sourcePS, the curve 2 corresponds to the intermediate state during thepolymerization, and curve 3 corresponds to the final polymer.

FIG. 2 shows the measurement results of FT-IR of the obtained polymer.The measurement was conducted by a KBr tablet method by means of theapparatus 1720X (Perkin Elmer Co.).

The absorption peaks a of Amide I are found at 1687 cm⁻¹ and 1653 cm⁻¹.The absorption peak a of Amide II is found at 1560 cm⁻¹. The absorptionpeaks b of the aromatic ether are found at 1262 cm⁻¹ and 1217 cm⁻¹.Thereby it was confirmed that the polymer had been formed by the amidelinkage.

Thermal decomposition characteristics were measured by thermogravimetry(TG) by TG-DTA 2000 S (MacScience Co.) in the temperature range up to500° C. at a temperature elevation rate of 10° C./min in N₂ gas. FIG. 3shows the measurement results. In FIG. 3, the curve A corresponds to thepolymer obtained in this Example, and the curve B corresponds to thecommercial PS.

FIG. 3 shows that the polymer of this Example has the same thermaldecomposition characteristics with the same thermal decompositioninitiation temperature and the same heat resistance as the PS (PS WakoJunyaku K.K.) having no amide linkage.

Example 11 Synthesis of Amide-Linked Polymer Having Spacer, 6

In a flask equipped with a nitrogen-introducing tube and a stirrer, wereplaced 10.0 g (0.4 mmol) of PS dicarboxylic acid having Mw of 50,000;80.25 mg (0.4 mmol) of 4,4′-diaminophenylmethane; 490 mg (0.8 mmol) oftriphenyl phosphite; and 60 mg of calcium chloride. The mixture in theflask was dissolved in 4 mL of NMP and 0.4 mL of pyridine. The solutionwas stirred at 100° C. for two hours in a nitrogen atmosphere. Theresulting polymer solution was poured into 400 mL of methanol, and thedeposited polymer was collected by filtration. The collected polymer wasrefluxed in 200 mL of methanol for one hour. Then the polymer wascollected by filtration and was dried in vacuo to obtain a white fibrouspolymer (Compound No. B-6). The weight-average molecular weight of thepolymer was 520,000 according to GPC measurement.

Example 12 Synthesis of Amide-Linked Polymer Having Spacer, 7

In a flask equipped with a nitrogen-introducing tube and a stirrer, wereplaced 12.5 g (0.25 mmol) of polyethylene-dicarboxylic acid having Mw of4,000; 54.1 mg (0.5 mmol) of p-phenylenediamine; 310 mg (1 mmol) oftriphenyl phosphite; 100 mg of lithium chloride; and 300 mg of calciumchloride. The mixture in the flask was dissolved in 5 mL of NMP and 1 mLof pyridine. The solution was stirred at 100° C. for 6 hours in anitrogen atmosphere. The polymer solution was poured into 300 mL ofmethanol, and the deposited polymer was collected by filtration. Thecollected polymer was refluxed in 150 mL of methanol for one hour. Thenthe polymer was collected by filtration and was dried in vacuo to obtaina white fibrous polymer (Compound No. B-7). The weight-average molecularweight of the polymer was 120,000 according to GPC measurement.

Example 13 Synthesis of Amide-Linked Polymer Having Spacer, 8

In a flask equipped with a nitrogen-introducing tube and a stirrer, wereplaced 10.0 g of polypropylene-dicarboxylic acid having Mw of 5,000; 80mg of p-xylenediamine; and 500 mg of triphenyl phosphite. The mixture inthe flask was dissolved in 4 mL of NMP and 1 mL of pyridine. Thesolution was stirred at 100° C. for 5 hours in a nitrogen atmosphere.The resulting polymer solution was poured into 400 mL of methanol, andthe deposited polymer was collected by filtration. The collected polymerwas refluxed in 200 mL of methanol for one hour. Then the polymer wascollected by filtration and was dried in vacuo to obtain a white fibrouspolymer (Compound No. B-8). The weight-average molecular weight of thepolymer was 90,000 according to GPC measurement.

Example 14 Synthesis of Amide-Linked Polymer Having Spacer, 9

In a flask equipped with a nitrogen-introducing tube and a stirrer, wereplaced 10.0 g of α-amino-1-carboxy-terminated-polyethylene (Mw 4,000);500 mg (0.8 mmol) of triphenyl phosphite; and 60 mg of lithium chloride.The mixture in the flask was dissolved in 5 mL of pyridine. The solutionwas stirred at 100° C. for 5 hours in a nitrogen atmosphere. Theresulting polymer solution was poured into 400 mL of methanol, and thedeposited polymer was collected by filtration. The collected polymer wasrefluxed in 200 mL of methanol for one hour. Then the polymer wascollected by filtration and was dried in vacuo to obtain a white fibrouspolymer (Compound No. B-9). The weight-average molecular weight of thepolymer was 20,000 according to GPC measurement.

Example 15 Synthesis of Ester-Linked Polymer Having No Spacer, 1

A 3-gram portion of α-hydoxy-ω-carboxy-terminated-polystyrene (Mw:50,000, Polymer Science Co.) was placed in a flask, and was heated to180° C. in a nitrogen atmosphere. Thereto, 35 mg of dibutyltin oxide wasadded and stirred. The formed water and diol were removed bydistillation at the temperature kept at 180-200° C. The reaction wascontinued at a reduced pressure. Then the reaction product was taken outfrom the flask while it was hot to obtain white polymer (Compound C-1).The weight-average molecular weight of the obtained polymer was 700,000according to GPC measurement. The number of the repeating units wasestimated to be about 14.

Examples 16 and 17 Synthesis of Ester-Linked Polymers Having No Spacer,2-3

Ester-linked polymers of Examples 16 and 17 were synthesized under thesame conditions as in Example 15 except that theα-hydroxy-ω-carboxy-terminated polystyrene was changed to a polystyrenehaving different molecular weight or to a polyethylene.

Examples 18 and 19 Synthesis of Amide-Linked Polymers Having No Spacer,1 and 2

Amide-linked polymers of Examples 18 and 19 were synthesized under thesame conditions as in Example 15 except that theα-hydroxy-ω-carboxy-terminated-polystyrene was changed intoα-amino-ω-carboxy-terminated-polystyrene or -polypropylene.

Table 3 shows the results of Examples 15 to 19.

For simplicity of representation, Synthesis Example is summarized as C-1in the table in which the linked polymer of the number of repeatingunits (n) of 14 was prepared fromα-hydorxy-ω-carboxy-terminated-polystyrene (Mw: 50,000, Mw representingweight-average molecular weight). Examples 16 to 19 are summarized inthe same style. Incidentally, in the case whereα-amino-ω-carboxy-terminated-polystyrene was used, R is represented byCONH. TABLE 3 Example Compound No. No. P R n 15 C-1 PS (50,000) COO 1416 C-2 PS (5000) COO 8 17 C-3 PE (20,000) COO 27 18 D-1 PP (4000) CONH 419 D-2 PS (10,000) CONH 21

Example 20 Synthesis of Amide-Linked Polymers Having No Spacer, 3

A 3-gram portion of β-amino-co-carboxy-terminated-polystyrene (Mw50,000) was placed in a flask, and was heated to 180° C. in a nitrogenatmosphere. Thereto, 35 mg of dibutyltin oxide was added and stirred.The formed water and diol were removed by distillation at thetemperature kept at 180-200° C. The reaction was continued at a reducedpressure. Then the reaction product was taken out from the flask whileit was hot to obtain white polymer (Compound D-3).

The weight-average molecular weight of the obtained polymer was 500,000according to GPC measurement.

Example 21 Synthesis of Urethane-Linked Polymer Having Spacer, 1

Distilled chlorobenzene and o-dichlorobenzene were mixed at a mixingratio of 80/20 (vol/vol). This mixed solvent was used as the reactionsolvent. A 3-gram portion of 1,4-butanediol and 120 mL of the solventwere placed in a four-neck flask equipped with a stirrer, a thermometer,a nitrogen-introducing tube, and a reflux condenser with a drying tubeattached. The flask was purged sufficiently with nitrogen, and then thenitrogen-introducing tube was changed to a dropping funnel with a dryingtube attached thereto. In the dropping funnel, were placed 5 g ofpolystyrene having a terminal isocyanate group at the respective ends,and 60 mL of the solvent. The flask was heated with stirring. With thestart of stirring, half of the content in the dropping funnel was addedin one lot to the flask with vigorous stirring. The remaining half ofthe dropping funnel content was added dropwise in 3 hours, andthereafter the reaction mixture was refluxed for one hour. After coolingto room temperature, the deposited polymer was collected by filtration.The polymer was dissolved in hot dimethylformamide. Thereto 50 mL ofmethanol was added and the mixture was left standing in a refrigeratorovernight. The reprecipitated polymer was collected by filtration andvacuum-dried (Compound No. E-1).

The weight-average molecular weight of the resulting polymer was300,000, and the polymerization degree was estimated to be about 30.

Examples 22 to 25 Synthesis of Urethane-Linked Polymers Having Spacer, 2to 5

The synthesis was conducted in the same manner as in Example 21 exceptthat the polymer moiety (P) of the polystyrene (PS) having terminalisocyanate groups at the respective ends was changed to a polystyrene ofa different molecular weight, polypropylene (PP), or polyethylene (PE),and the 1,4-butanediol was changed to another diol compound.

Table 4 shows specifically Examples 21 to 25.

For simplicity of representation, Synthesis Example of Example 21 issummarized as E-1 in the table, in which the linked polymer of thenumber of repeating units (n) of 30 was prepared from 1,4-butanediol andpolystyrene having a terminal isocyanate group at the respective ends(Mw: 10,000, Mw representing weight-average molecular weight). Examples22-25 are summarized in the same style. TABLE 4 Example Compd R No. No.P X1 A X2 n 21 E-1 PS OCONH 1,4-C₄H₈ NHOCO 30 (10,000) 22 E-2 PS OCONH1,12-C₁₂H₂₄ NHOCO 22 (5,000) 23 E-3 PP OCONH C₂H₄ NHOCQ (50,000) 24 E-4PE (10,000) OCONH

NHOCO 6 25 E-5 PS OCONH 1,8-C₉H₁₈ NHOCO 12 (25,000)

Example 26 Synthesis of Urea-Linked Polymer Having Spacer, 1

Chlorobenzene and o-dichlorobenzene both having had been distilled weremixed at a mixing ratio of 80/20 (vol/vol). This mixed solvent was usedas the reaction solvent. A 3-gram portion of hexane-1,6-diamine and 120mL of the solvent were placed in a four-neck flask equipped with astirrer, a thermometer, a nitrogen-introducing tube, and a refluxcondenser with a drying tube attached. The flask was purged sufficientlywith nitrogen, and then the nitrogen-introducing tube was changed to adropping funnel with a drying tube attached thereto. In the droppingfunnel, were placed 5 g of polystyrene having an isocyanate group at therespective ends (Mw 5000), and 60 mL of the solvent. The flask washeated with stirring. With the start of the stirring, half of thecontent in the dropping funnel was added in one lot to the flask withvigorous stirring. The remaining half of the dropping funnel content wasadded dropwise in 3 hours, and thereafter the reaction mixture wasrefluxed for one hour. After cooling to room temperature, the depositedpolymer was collected by filtration. The polymer was dissolved in hotdimethylformamide. Thereto 50 mL of methanol was added and the mixturewas left standing in a refrigerator overnight. The reprecipitatedpolymer was collected by filtration and vacuum-dried (Compound No. F-1)

The weight-average molecular weight of the resulting polymer was 100,000according to GPC measurement, and the number of the repeating units (n)was estimated to be about 20.

Table 5 shows specifically Examples 26.

For simplicity of representation, Synthesis Example of Example 26 issummarized as F-1 in the table in which the urea-linked polymer of thenumber of repeating units (n) of 20 was prepared from hexane-1,6-diamineand polystyrene having an isocyanate group at the respective ends (Mw:5,000, Mw representing weight-average molecular weight). TABLE 5 ExampleCompd R No. No. P ×1 A ×2 n 26 F-1 PS NHCONH 1,6-C₆H₁₂ NHCONH 20 (5,000)

Examples 27 to 33 Molding

The powdery polymers synthesized in the above Examples were molded bythe methods shown in Table 6, As a result, satisfactory molded articleswere obtained. TABLE 6 Exam- ple Poly- No. mer Method Conditions Shape27 B-4 Compres- 200° C., 3 MPa Square plate sion 20 cm × 20 cm × 3 mm 28D-4 Compres- 200° C., 3 MPa Square plate sion 20 cm × 20 cm × 3 mm 29C-1 Extrusion 220° C., 100 rpm Round bar Single screw 5 mm φ 30 A-1Injection 220° C. (Tip) Cup Inj. pressure 5 cm φ × 7 cm 90 MPa 1 mmthick 31 B-5 Compres- 200° C., 3 MPa Square plate sion 20 cm × 20 cm × 3mm 32 B-9 Extrusion 210° C., 100 rpm Round bar 5 mm φ Single screw 33B-6 Injection 220° C. (Tip) Cup Inj. pressure 5 cm φ × 7 cm 80 MPa 1 mmthick

Example 34 Recycling

The molded article formed in Example 30 was crushed. A 10-gram portionof the crushed matter was dissolved in 400 mL of toluene. Thereto 400 mLof aqueous 1-mol/L (1N) sodium hydroxide solution was added. The mixturewas stirred at 100° C. for 24 hours. The molecular weight of the polymerwas confirmed by GPC to have decreased to the value of the startingpolystyrene polymer. After removal of the solvent by distillation, therecovered matter was washed with aqueous 10% acetic acid solution,further washed with ethanol, and dried. The recovered matter wasconfirmed to be a polystyrene derivative by infrared spectrometry. Therecovered powdery matter was treated for the synthesis in the samemanner as in Example 1. Thereby the same results were obtained.

Example 35 Recycling

The molded article formed in Example 31 was crushed. A 10-gram portionof the crushed matter was dissolved in 300 mL of xylene. Thereto 100 mLof 94% sulfuric acid was added, and the mixture was stirred at 110° C.for 27 hours. FIG. 4 shows the differential curves of the molecularweight distribution. In FIG. 4, curve 4 corresponds to the moldedpolymer article, curve 5 corresponds to a treated polymer after 7 hoursfrom starting the treatment, and curve 6 corresponds to the recycledmatter. As shown in FIG. 4, it was confirmed by GPC that the molecularweight of the polymer decreased to the value of the starting polymer ofstyrene polymer. After removal of the solvent by distillation, therecovered matter was washed with aqueous 1-mol/L (1N) sodiumhydrogencarbonate solution, further washed with ethanol, and dried. Therecovered matter was confirmed by infrared spectrometry to be apolystyrene derivative. The recovered powdery matter was used for thesynthesis in the same manner as in Example 10, whereby the same resultswere obtained.

Example 36 Synthesis of Polymer, 1

A styrene polymer having a carboxyl group at the respective ends andhaving a molecular weight of 25,000 is employed as the polymer havingtwo condensable functional groups. Butanediol was employed which has twofunctional groups linkable to the two carboxyl groups, as the couplerfor the aforementioned polymer. These compounds are heated to 180° C. ina flask. Thereto, titanium isopropoxide is added in an amount of 0.5mass % as the catalyst with stirring. The reaction flask is purged bygaseous nitrogen and evacuated gradually to 6.67 kPa to remove the waterformed by the dehydration condensation. After 3 hours of reaction, thepolymer is recovered.

(Decomposition of Polymer, 1)

The synthesized polymer is dissolved N,N′-dimethylformamide (DMF) at aconcentration of 10 mass %. Thereto, 1 mol/L (1N) hydrochloric acid isadded and the mixture is stirred at 40° C. for 5 hours to hydrolyze thepolymer. In the hydrolysis, the compound represented by StructuralFormula (6) below is added thereto in an amount of 0.1% as the compoundhaving a condensable functional group and a spin-trapping group.

The resulting styrene polymer having a carboxyl group at the respectiveends of the molecule and having a molecular weight of 25,000 isrecovered by repetition of dissolution in toluene and precipitation bymethanol. The butanediol formed by the decomposition is recovered bydistillation.

(Resynthesis of Polymer, 1)

A polymer is synthesized by using, as the starting materials, therecovered styrene polymer having a carboxyl group at the respective endsand having a molecular weight of 25,000 and butanediol, in the samemanner as in “Synthesis of Polymer, 1” described above.

The polymer obtained in “Synthesis of Polymer, 1” and the polymerobtained in “Resynthesis of Polymer, 1” are confirmed to be equivalentby molecular weight distribution measurement by GPC.

Example 37 Molding of Polymer, 1

The polymer having been synthesized in Example 36 “Synthesis of Polymer,1” is used as a molding material for molding with addition of thecompound represented by Structural Formula (7) as the compound having acondensable functional group and a spin-trapping group in an amount of1%.

This molding material is extrusion-molded at 180° C. into a printercase.

(Decomposition of Polymer, 2)

The molded polymer is hydrolyzed in the same manner as in “Decompositionof Polymer, 1” in Example 1. In the hydrolysis of this Example, thecompound of Structural Formula (7) having a condensable group and aspin-trapping group need not necessarily be added newly since thecompound has been already added.

(Resynthesis of Polymer, 2)

A polymer is produced from the recovered material in the same manner asin “Resynthesis of Polymer, 1”. The molecular weight distribution of theresynthesized polymer and that of the polymer before the moldingoperation are confirmed to be equivalent by GPC.

Example 38 Synthesis of Polymer, 2

Two styrene polymers are employed: one having a carboxyl group at therespective ends of the molecule and having a molecular weight of 25,000,and another having a hydroxyl group at the respective ends of themolecule, as the polymers having two condensable functional groups.These compounds are heated together to 180° C. in a flask. Thereto,titanium isopropoxide is added in an amount of 0.5 mass % as thecatalyst. The reaction flask is purged by gaseous nitrogen and evacuatedgradually to 6.67 kPa to remove the water formed by the dehydrationcondensation. After 5 hours of the reaction, the polymer is recovered.

(Decomposition of Polymer, 3)

The synthesized polymer in “Synthesis of Polymer, 2” is dissolvedN,N′-dimethylformamide (DMF) at a concentration of 10 mass %. Thereto,1-mol/L (1N) hydrochloric acid is added and the mixture is stirred at40° C. for 5 hours to hydrolyze the polymer. In the hydrolysis, acompound represented by Structural Formula (6) described in Example 36is added thereto in an amount of 0.1% based on the polymer as thecompound having a condensable functional group and a spin-trappinggroup.

The resulting styrene polymers, one having a carboxyl group at therespective ends of the molecule and having a molecular weight of 25,000,and the other one having a hydroxyl group at the respective ends of themolecule and having a molecular weight of 25,000, are recovered byrepetition of dissolution in toluene and precipitation by methanol.

(Resynthesis of Polymer, 3)

A polymer is synthesized by dehydration condensing the styrene polymerhaving a carboxyl group at the respective ends of the molecule andhaving a molecular weight of 25,000 and the one having a hydroxyl groupat the respective ends of the molecule and having a molecular weight of25,000 which have been recovered in the above “Decomposition of Polymer,3”, in the same manner as in “Synthesis of Polymer, 2” described above.

The polymer has the molecular weight and molecular weight distributionequivalent to the polymer obtained in “Synthesis of Polymer, 2”.

Example 39

(Recycling Method)

The polymer obtained in Example 36 is molded in the same manner as“Molding of Polymer, 1” in Example 37 into a printer case. The moldedproducts after use are collected from users. A part of the collectedcases are decomposed by the method of “Decomposition of Polymer, 1” ofExample 36 to obtain newly a source material for polymer synthesis. Fromthis material, a polymer is synthesized newly by the method of“Resynthesis of Polymer, 1” of Example 36. Separately, the remainder ofthe collected cases are chipped without preliminary treatment, andformed by a sandwich-molding into printer cases by the method describedin Japanese Patent Publication No. 6-24739 (Patent Literature 1).

These recycling steps may be conducted by one and the same company, ormay be shared by plural companies.

Reference Example 1

(Decomposition of Polymer 4)

The polymer obtained in Example 36 is hydrolyzed in the same manner asin “Decomposition of Polymer 1” in Example 36 except that the compoundof Structural Formula (6) is not added. Thereby the styrene polymerhaving a carboxyl group at the respective ends and butanediol arerecovered.

(Resynthesis of Polymer, 4)

From the recovered styrene polymer having a carboxyl group at therespective ends and butanediol, a polymer is synthesized in the samemanner as in “Resynthesis of Polymer, 1” in Example 36.

The polymer obtained in “Synthesis of Polymer, 1” in Example 36 and thepolymer obtained this “Resynthesis of Polymer, 4” are subjected to GPCmeasurement to compare the molecular weight distribution. As theresults, the polymer obtained in “Resynthesis of Polymer, 4” has a lowermolecular weight.

The present invention provides a novel polymeric material synthesizableand decomposable reversibly. Further, the decomposition-resynthesistechnique of the present invention enables a novel material-recyclingsystem with less energy input. Furthermore, the present invention, bybeing combined with any of reuse technique, material-recyclingtechnique, chemical recycling technique, thermal recycling technique andso forth, enables remarkably effective use of source materials incomparison with conventional techniques, and contributes greatly toconstruction of sustainable society.

1. A polymer represented by Structural Formula[—P₁—R—]_(n)  (1) wherein P₁ is an addition polymer moiety having acontinuous hydrocarbon skeleton containing no condensation system andformed by addition polymerization of one or more monomers having adouble bond; R is a linking moiety comprising a condensation system; andn is a number of repeating units and is an integer of 2 or more.
 2. Thepolymer according to claim 1, wherein the linking moiety R is selectedfrom the group consisting of —CO—O—, —CONH—, —NH—CO—O— and —NH—CO—NH—.3. The polymer according to claim 1, wherein linkage sites of Rrepresented by a bond between P₁ and R in a repeating unit of theStructural Formula (1) are the same throughout the repeating units. 4.The polymer according to claim 1, wherein linkage sites of R representedby a bond between P₁ and R in the repeating unit of Structural Formula(1) are different between adjacent repeating units.
 5. The polymeraccording to claim 1, wherein linkage sites of R represented by a bondbetween P₁ and R in the repeating unit of Structural formula (1) are thesame or different between two adjacent repeating units.
 6. The polymeraccording to claim 1, wherein the linking moiety R is represented byStructural Formula (2):X₁-A-X₂  (2), wherein X₁ and X₂ are, independently, an atomic grouplinked to P₁ in the Structural formula (1), and A is an atomic groupcapable of linking with X₁ and X₂.
 7. The polymer according to claim 6,wherein X₁ and X₂ are independently selected from the group consistingof —CO—O—, —CONH—, —NH—CO—O— and —NH—CO—NH—.
 8. The polymer according toclaim 6, wherein X₁ and X₂ are the same atomic group.
 9. The polymeraccording to claim 6, wherein the atomic groups X₁ and X₂ are differentfrom each other.
 10. The claim according to claim 6, wherein linkagesites of X₁ and/or X₂ to A may be the same or different between twoadjacent repeating units.
 11. The polymer according to claim 6, whereinlinkage sites of X₁ and/or X₂ to A are the same throughout the repeatingunits.
 12. The polymer according to claim 1, wherein the additionpolymer moiety P₁ is at least one moiety selected from the groupconsisting of polystyrene, polybutadiene, polyacrylonitrile,polyethylene and polypropylene.
 13. The polymer according to claim 6,wherein the group A is an alkylene group.
 14. A molded article formed bymolding the polymer set forth in claim
 1. 15. A process for producingthe polymer represented by Structural Formula (1), comprisingcondensation-polymerizing an addition-polymer having a functional groupat each end thereof solely or in a manner of making a two-functionalcompound intervening therebetween:[—P₁—R—]_(n)  (1) wherein P₁ is an addition polymer moiety having acontinuous hydrocarbon skeleton containing no condensation system andformed by addition polymerization of one or more monomers having adouble bond; R is a linking moiety comprising a condensation system forlinking plural P₁; and n is a number of repeating units and is aninteger of 2 or more.
 16. The process for producing the polymeraccording to claim 15, wherein the process further comprises a step ofmolding the polymer represented by the Structural formula (1).